I am not sure this will answer your question or provide you with comments you are looking for but here is my take on the Swing Plane. It is kind of long and rambles a bit.
My thoughts and understanding of the Swing Plane....
Swing Plane, On Plane are all terms we use when discussing the golf swing. But do we really know what the swing plane is? How do we know that we are On Plane? Do all golfers use the same Swing Plane? Is a flat swing plane or an upright swing plane at fault for poor golf shots?
Plane Angle is defined by the Golf Club Lie Angle. In order for the golf club as designed to make centered contact the sole of the club head should be parallel to the ground. (Toe and Heel same distance from the ground.) Tilting of the clubhead will change the Ball Flight's characteristics ranging from loss of distance, inaccuracy, and abnormal trajectory. Note - there is a line from the grip to the center of the sweet spot on the golf club face which is referred to as the sweet spot plane. THIS angle is the near ideal angle which should be used as the Plane Angle. You may recall seeing golfers who actually ground the club with the toe up a bit. This satisfies the sweet spot plane line angle and also can account for any possible club head droop that may occur.
Plane is a flat surface and is 2 dimensional
Swing Plane is a flat surface that is Inclined and is 3 dimensional.
Plane Line is a straight line extended from the ball toward the ball and behind the ball.
The Golf Swing is 3 dimensional
- Back Stroke moves the golf club Backward, Upward and Inward.
- Down Stroke moves the golf club Downward, Forward and Outward.
- Forward Stroke moves the golf club Upward, Backward and Inward.
(Note the shoulder rotation is responsible for the Inward and Outward motion, and the Arms are responsible for the Backward, Upward, Downward and Forward motion)
The Swing Plane angled that is defined by the club shaft lie angle does not have to be maintained through out the swing for the golfer to be on plane. The golfer can shift be between Swing Plane angles so long as the Plane Line remains the constant. The golfer would be considered to be On Plane. At Impact, ideally at hip level during the down stoke the golfer will have returned the club back to the originally defined club lie angle.
FINDING the SWEET SPOT Plane Line (this can vary between clubs within the same set.) Using a string with heavy pointed object attached at one end hanging down near the clubhead, hold the other end at the grip end on center line of the front of the grip. With the pointed object dangling at the face and club held vertically, note the place on the face it points too. Now from the point back to the center of the shaft at the top of the grip defines the Sweet Spot Plane Line. When soling the golf club at address, this is the IDEAL angle the clubshaft should be set too.
Determine if you are On Plane (this is a method you can use to determine if you are on plane). First how is On Plane defined through out the golf swing; At all times in the swing if the golf club is to be on plane the golf shaft must either be pointing to the Plane Line or parallel to the Plane Line. When the golf shaft is parallel to the ground, at hip levels or at the top of the swing(if the golf club reaches parallel to the ground at the top) it should be parallel to the Plane Line. At all other times the closest part of the club, clubhead or grip butt, should always be pointing to the Plane Line.
Lazer Training Aids are based on the above principle.
You can make your own training aid but remember this training aid or even the lazer training aid must be used in low light area. They don't work well in bright light, especially sun light.
I found an inexpensive mag lite that used a triple A battery and had an adjustable light focus capability. Two pieces of velcro, I attached it to the shaft just below the golf grip. I then placed several clubs behind the ball pointing towards the target to use as a line. Turn the light on, adjust to a narrow focus and practice the swing in slow speed. Most golfers who first try this find that they feel they are pushing the club away from the body to the outside when in actually they are on plane. You can reverse the direction of the light or get a second light and place a club or two in front of the ball as well and trace the entire swing. Also this can be done using the key ring lazer light, but they are about as twice as expensive.
An alternative to building your own in my opinion is to buy one, I would suggest you consider the Ez Swing Plane Trainer (about $60).
Additional Thoughts and Clarification:
On Plane is when the club shaft is either pointing to the plane line or parallel to the plane line. Golfers who take the club upright still have the club shaft having this relationship with the plane line but the plane angle is different that of the club lie angled defined.
Right forearm on plane (usually primary factor is to match the club lie angle prior to impact, most likely starting at hip level during the down stroke) is something both hitters and swingers want and need. Without the right forearm this plane the power of the right side is compromised and it requires additional adjustment if the club is to be presented to the ball on plane. Overall for either it becomes a weaker shot that can have accuracy problems. Only time that this would not be true is when the right elbow replace the left shoulder as the center of the clubhead arc.
The Plane Line is what I use to measure On Plane throughout the entire swing. Usually above parallel golfers shift but remain On Plane cause the club shaft maintains it relationship to the Plane Line.
Personal opinion... I think that there has been considerable confusion added, possible misinformation, information out of context that is not allowing a golfer to develop a clear understanding and picture of the golf swing and especially regarding thier own golf swing.
Left arm, right arm, shoulder, hip, everything but breathing in or out on the rest period of the heart or the beat.
Speaking of the left arm and right arm. Add the shoulders and we have the Triangle. The right arm is the only factor is changing the triangle. This says the shoulders don't change regarding width during the swing. This says the Left arm doesn't change during the swing.
I would say no golfer should just change thier understanding of the golf swing, especially mechanics till they can demonstrate to themselves that what they are changing and doing is correct.
Your acknowledgement of shift, I may be just misunderstanding, but as I see them they remain On Plane, just a different Plane angle.
Not the greatest artist but here is my concept
I am working a better Diagram, From hip to top I need to show the plane angle shift, but still remains on plane.
